1. Field of the Invention
The present invention relates to a shutter unit for a vehicle, provided on a front part of a vehicle, for adjusting an amount of outside air introduced into the front part.
2. Description of the Related Art
Conventionally, a shutter unit for a vehicle of this kind has been proposed in Japanese Laid-Open Utility Model Publication (Kokai) No. S59-114412. This shutter unit is for adjusting a flow rate of outside air flowing through a radiator which cools an internal combustion engine of a vehicle, and is disposed in a front grill of the vehicle. Further, the shutter unit comprises a shutter formed by a plurality of pivotally movable blades and driving means. The driving means opens and closes the shutter, to thereby adjust the flow rate of outside air flowing through the radiator. Further, the shutter is provided with a spring for urging the shutter toward an open position. In this conventional shutter unit, even when the driving means is faulty, the spring returns the shutter to the open position to thereby ensure cooling capacity of the radiator.
However, the shutter of this kind is provided on the front part of the vehicle and is exposed to outside air, and hence particularly, foreign matter, such as dust, is likely to attach to the shutter. For this reason, in the conventional shutter unit, there is a fear that the shutter is stuck by attached foreign matter, and as a result, the shutter cannot be moved even by urging of the spring, which makes the shutter faulty. However, in the conventional shutter unit, the shutter is merely provided with the spring in order to compensate for a failure of the driving means, and hence it is impossible to determine such a failure of the shutter as described above.